The invention relates to a variable swirl generating intake manifold with at least one longitudinally oriented partition wall that forms at least one swirl generating first manifold section and one swirl stopping second manifold section, said manifold sections only meeting again in the valve area, at least the second manifold section being, for the purpose of increasing the swirl, at least partially closable in the entrance area by means of a control flap that is pivotal about an axis, said axis being substantially arranged in the plane of the partition wall, said control flap having two arms and said two manifold sections being at least partially closable in a first rotational end position and open in a second rotational end position.
The document EP 0 258 207 B1 discloses an intake manifold for internal combustion engines with a longitudinally oriented partition wall. In order to achieve a strong enough swirl flow within the cylinder at part load on the one hand and the best possible filling of the cylinder at high speed on the other hand, the partition wall is arranged parallel to the cylinder""s axis in an intake manifold that actually generates a very low swirl level. If a swirled flow is desired at part load, one manifold section is closed by a control flap. This results in an asymmetric flow through the valve into the cylinder and, through interaction with the cylinder""s wall, the charge is caused to strongly rotate. In its closed condition, the flap is positioned crosswise to the flow and creates turbulence within the intake manifold. It is not possible to vary the cross-sectional area of the flow of the other intake manifold.
U.S. Pat. No. 4,381,743 discloses a variable area swirl generating inlet manifold of an internal combustion engine that is provided with a partition wall made from a thin, flexible material. The cross-sectional area of the flow path, and accordingly the swirl produced, may be varied in bending the partition wall. The flexible wall only permits to vary part of the cross-sectional area of the manifold.
The document WO 95/17589 A1 discloses a variable swirl generating intake manifold with two manifold sections that are separated by a partition wall, a control flap with two arms being realized in an effort to increase the swirl, said control flap opening the two manifold sections in a first end position and partially closing them in a second end position. The control flap is provided with a grid structure in the region of the swirl generating manifold section. Limited control of the flow path is only possible in conjunction with a variation in the swirl.
The publication JP 2000-328948 A discloses an intake control device for an internal combustion engine. An intake manifold is thereby divided into two manifold sections by means of a partition wall made from a flexible material. The inlet swirl may be regulated by bending the partition wall. The flow path is controlled by way of a conventional throttle.
The document DE 37 33 441 C1 describes a check valve arrangement in the intake manifold of a quantity controlled internal combustion engine. The intake manifold is provided with two manifold sections, spring fins for varying the flow path being arranged in each manifold section. Spring-biased curved wedges act on the spring fins and bring them into the position that closes the intake manifold when the intake valve is closed. A drawback thereof is that, to actuate the curved wedges, one spring fin and one camshaft are required for each manifold section, which increases the expenditure for installation and assembly. Another disadvantage is that, compared with a control flap, more space and more constructional modifications are needed.
It is the object of the invention to permit in the simplest possible way to both vary the swirl and control the flow path.
This is achieved in accordance with the invention in that, for providing an increase in swirl, the control flap may be deviated from the second rotational end position toward a third end position by closing at least partially the second manifold section.
It is particularly advantageous when the control flap may be deviated from the second rotational end position toward the third end position in an elastic manner, preferably by bending. To increase the swirl, the control flap is thereby bent into the third end position, the second manifold section being substantially closed. The essential point is that the deformation of the control flap in the direction of the variation in swirl may be performed exerting as little force as possible. To achieve this, it is advantageous to have the control flap provided with a predetermined bending point preferably located in the neighborhood of the axis, said predetermined bending point being preferably formed by definingly thinning the material. When actuated in the opposite direction, i.e., in the direction of the second rotational end position, in order to reduce the swirl, the control flap should exhibit highest possible rigidity. For this purpose, there is preferably provided that, starting from the second rotational end position, the control flap is less resistant to deflection in the direction of the third end position than in the direction of the first rotational end position. To provide the control flap with a direction dependent deflection resistance, the control flap may be convex curved preferably toward the side of the first manifold section. The predetermined bending point itself can be formed by locally thinning the material. It is particularly advantageous when the predetermined bending point is formed by at least one slot moulded in the control flap to the side of the first manifold section, said slot being oriented substantially parallel to the axis. By virtue of the slot in the control flap, said control flap is more resistant to deflection when caused to move in the direction of the slotted side than when caused to move in the opposite direction.
In a particularly preferred variant of the invention, the control flap is bipartite and it is preferred that the two parts of the bipartite control flap be elastically connected together. The two parts of the control flap may also at least partially be encased, the elastic casing joining the two parts together.
In another variant of the invention there is provided that the two parts are joined together in the region of the axis by means of an axial spring element. Without departing from the scope of the invention there may furthermore be provided that the first flap arm, which is arranged upstream from the axis, is larger than the second flap arm arranged downstream of the axis, the rotational movement of the control flap in the second rotational end position being preferably limited by a stop and the second flap arm preferably abutting on the partition wall.
More specifically in internal combustion engines in which one exhaust gas recirculation manifold discharges into every intake manifold it is advantageous when, between axis and partition wall, a blow-by is realized between the first and the second manifold section, said blow-by being at least mainly closed in the second rotational end position of the control flap by way of preferably the second flap arm. Accordingly, the blow-by may be controlled by the second flap arm. A particularly high flexibility in controlling the intake manifold may be achieved when the blow-by, in the first rotational end position of the control flap, may be closed by a flap element that is actuable independent of the control flap. In this manner, the blow-by can be actuated largely independent of the control flap when the control flap is in the first rotational end position.
The actuation of the control flap can be substantially simplified when a restoring force, which is preferably produced by a return spring, is applied onto the control flap in the direction of the second rotational end position.
The control flap itself may be made from a temperature resistant plastic, such as carbon fiber reinforced plastic for example, or from steel plate like e.g., spring steel, or from a sheet steel-plastic composite material.
To still permit a residual flow to pass through the intake manifold when the control flap is in the first rotational end position, said control flap is provided, at least in the region of one flap arm, with a leakage port or with a leakage recess.
The actuation device for the control flap may be electromechanical, electrohydraulic, electropneumatic, electromagnetic or have a bimetal element and one actuation device can be provided either for each of the intake manifolds or for a group of intake manifolds.